1. Field of the Invention
The present invention relates to a vibration motor.
2. Description of the Related Art
Vibration motors have been used in various devices, such as smartphones. An example of existing vibration motors is disclosed in CN 202435225 U.
The vibration motor described in CN 202435225 U includes a vibrating body, which includes two magnets, and a coil, which is fixed to a casing. When driving the vibration motor, a magnetic field is generated between the magnets and the coil, and the vibrating body vibrates. The vibration motor described in CN 202435225 U further includes a top plate portion. The top plate portion is disposed above the vibrating body in an up-down direction that is perpendicular to one direction in which the vibrating body vibrates. The top plate portion faces the magnets. The top plate portion functions as a back yoke for suppressing leakage of magnetic flux between the two magnets.
In recent years, haptic technology, which is a technology for transmitting information through tactile sensation, has been improved. Thus, vibration motors are required to have a function of transmitting small vibrations for tactile feedback and the like, in addition to a vibration function that has been used for silent notification.
A vibration motor used for tactile feedback and the like needs to start and stop sharply, because high responsiveness is required for such purposes. It may be possible to increase the speed of starting and stopping of the vibration motor by increasing the magnetic force of a magnet. However, in the vibration motor described in CN 202435225 U, even if the magnetic force is increased by using large magnets, it is not possible to form a magnetic path between the two magnets without increasing the thickness of the top plate portion. If the thickness of the top plate portion is increased, the thickness of the entirety of the vibration motor is increased, and reduction in the thickness of the vibration motor is hindered.